JP3093221B2 - Image processing device - Google Patents

Description

The present invention relates to an image processing apparatus, and more particularly, to an image processing apparatus.
The present invention relates to an image processing apparatus capable of generating a three-dimensional shape and a cross-sectional shape of a target object viewed from an arbitrary viewpoint.

[Prior Art] FIG. 4 shows a processing flow of a conventional image processing apparatus of this type.

First, an original slice image is input and stored. The original slice image is obtained by, for example, a CT apparatus or an MRI apparatus.

Next, the original slice image is binarized by comparing the threshold value set by the operator with the pixel value of each slice image, and an area having a pixel value larger than the threshold value is extracted (P2).

Next, voxel data is created by stacking the regions extracted from each slice image (P3).

Next, projection conversion is performed assuming a projection plane perpendicular to the direction of the viewpoint set by the operator (P4).

 Next, the hidden surface is removed by the Z buffer method (P5).

 Next, shading is applied (P6).

As described above, it is possible to obtain a surface display image in which the object including the portion larger than the threshold is viewed from the set viewpoint (P7).

The above prior art is disclosed in, for example, "Medical Image Diagnosis Apparatus Yoshinori Iwai and others Corona P65-P67".

[Problem to be Solved by the Invention] In the above-mentioned conventional image processing apparatus, a slice image is binarized by threshold processing to extract an area.

However, for this reason, there is a problem that the shade information of the pixel value is lost. Specifically, there is no problem in displaying the surface of a homogeneous target object such as a skull, but it is difficult to obtain a good image of a partially shaded target object such as a brain or a nerve. become.

Accordingly, an object of the present invention is to provide an image processing apparatus capable of displaying a three-dimensional image of a target object viewed from an arbitrary viewpoint while maintaining the density information of the original slice image.

[Means for Solving the Problems] An image processing apparatus according to the present invention includes an original slice image group storage unit that stores an original slice image group of a target object, and a viewpoint direction for inputting a viewpoint direction for viewing the target object. Input means, a reforming means for generating a new slice image group re-sliced on a plane perpendicular to the viewpoint direction based on the original slice image group, and a pixel value and a predetermined threshold value for the new slice image group. It is characterized by comprising an interest extracting means for extracting a portion of interest by comparison and a hidden surface removing means for performing hidden surface removal processing on the extracted part of interest by a Z-buffer method.

It is preferable that a weighting means for multiplying the pixel value by a coefficient corresponding to the position of the pixel in the viewpoint direction to perform weighting is provided before or after the part of interest extraction means.

[Operation] The image processing apparatus according to the present invention generates a new slice image group re-sliced from the original slice image group of the target object on a plane perpendicular to the viewing direction of the target object.

Then, the pixel value is compared with a predetermined threshold value for the new slice image group, and a portion of interest is extracted.

Then, the extracted part of interest is subjected to hidden surface removal using the Z-buffer method to obtain a three-dimensional image.

In this way, the part of interest is extracted by the threshold,
Since the binarization is not performed and the pixel value is stored, a three-dimensional image viewed from an arbitrary viewpoint can be obtained while the grayscale information is stored.

Since voxel data is not created, shading becomes difficult, but the same effect can be obtained by multiplying a pixel value by a coefficient corresponding to the position of the pixel in the viewpoint direction and performing weighting. And a natural image can be obtained.

[Example] Hereinafter, the present invention will be described in more detail based on an example shown in the drawings. It should be noted that the present invention is not limited by this.

In the image processing apparatus 1 according to one embodiment of the present invention shown in FIG. 1, an original slice image obtained by, for example, an X-ray CT apparatus or the like is stored in an original slice image storage device 2.

The trackball 3 is for inputting a viewpoint direction and a viewpoint position. In addition, the viewpoint direction and viewpoint position can be input using a mouse or the like. The viewpoint position is
It can be set not only outside the target object but also inside the target object.
When the viewpoint position is placed outside the target object, a three-dimensional surface image is obtained. On the other hand, when the viewpoint position is placed inside the target object, the image becomes a three-dimensional image viewed from a cross section cut along a plane including the viewpoint position and perpendicular to the viewpoint direction.

The three-dimensional address generator 4 generates a three-dimensional address for reslicing the original slice image on a plane perpendicular to the viewpoint direction.

FIG. 3 conceptually shows the re-slicing of the slice. When the original slice image group 20 and the viewpoint direction A are given, the slice is re-sliced on a plane perpendicular to the viewpoint direction A, and a new slice image is obtained. Group 30 is obtained.

When the pixel value corresponding to the address generated by the three-dimensional address generator 4 cannot be obtained from the original slice image, the interpolation calculator 5 performs an interpolation operation to calculate the pixel value of the address.

As the three-dimensional address generator 4 and the interpolation calculator 5, a conventionally known reforming device can be used.

The comparison calculator 6 compares the threshold value input from the keyboard 7 with the pixel value of the new slice image, and extracts only a region having a pixel value larger than the threshold value, that is, a portion of interest.

The coefficient multiplier 8 weights the pixel value by multiplying the pixel value of the part of interest by a coefficient corresponding to the distance from the viewpoint position to the position of the pixel. For example, if a coefficient having a smaller value is used as the distance increases, the image becomes brighter near the viewpoint and darker as the distance increases, so that naturalness of the image can be obtained. The Z coordinate value of each address of the first new slice image is stored in the Z buffer 9, and the pixel value is stored in the image buffer 10.

After finishing the processing of the first new slice image, the system control device 11 reslices the original slice image group on a new plane in which the Z coordinate value is increased by a pitch corresponding to the resolution of the slice image. It instructs the three-dimensional address generator 4.

In the second new slice image, hidden surface removal processing is performed in the Z buffer 9 by the Z buffer method. That is, the Z coordinate value of the second new slice image is written only at the position where the Z coordinate value is not stored in the first new slice image, and the pixel value is written to the image buffer 10 correspondingly.

 Hereinafter, the above processing is repeated.

When a new slice image cannot be generated, a three-dimensional image of a part of interest viewed from the viewpoint position set by the trackball 3 is obtained in the image buffer 10. This 3
The three-dimensional image holds pixel values, and a three-dimensional image of a target object such as a brain or nerve can be suitably obtained.

In the image processing apparatus 1, the coefficient multiplier 8 is provided after the comparison calculator 6. However, the coefficient multiplier 8 may be provided before the comparison calculator 6.

FIG. 2 is a flowchart specifically showing the operation of the image processing apparatus 1.

 In step S1, the original slice image is stored.

In step S2, when the viewpoint is outside the space of the original slice image group, a plane perpendicular to the line-of-sight direction is brought closer to the space of the original slice image from the viewpoint position, and the slice image obtained by first cutting the space of the original slice image Is created. Also,
When the viewpoint position is in the space of the original slice image group, a new slice image is created by cutting the space of the original slice image by a plane perpendicular to the viewpoint direction and passing through the viewpoint position.

In step S3, each pixel of the new slice image is extracted, and the pixel value is compared with a threshold value. When the pixel value is smaller than the threshold value, the next pixel value is extracted, and when there are no more pixels in the new slice image, the next new slice image is created and the first pixel is extracted. If the process reaches the last pixel (step S6), the process ends (step S7).

If the pixel value is equal to or larger than the threshold value, the process proceeds to step S4, where the pixel value is multiplied by a coefficient corresponding to the distance from the viewpoint.

In step S5, the pixel value is stored as data only when the pixel is closest to the viewpoint by the Z-buffer method.

In step S6, if the next pixel can be extracted from the new slice image or if the next new slice image can be created, the process returns to step S2. If neither is possible, it is the end of the data and the processing is ended.

Thus, in step S7, a three-dimensional image of the part of interest viewed from the set viewpoint is obtained.

[Effect of the Invention] According to the image processing apparatus of the present invention, a three-dimensional image of a portion of interest can be obtained without creating voxel data.
Further, since the pixel values can be stored, a three-dimensional image can be formed without losing the grayscale information. Furthermore, if the position of the viewpoint is set inside the target object, a three-dimensional image cut by a plane passing through the viewpoint can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image processing apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart of an operation according to an embodiment of the present invention, and FIG. 3 shows a relationship between an original slice image group and a new slice image group. FIG. 4 is a flowchart showing the operation of the conventional image processing apparatus. (Explanation of reference numerals) 1... Image processing device 2... Original slice image storage device 3... Trackball 4... 3D address generator 5... Interpolation calculator 6... Comparison calculator 7. ... Coefficient multiplier 9... Z buffer, 10... Image buffer 11... System controller 20... Original slice image group 30.

Claims (1)

(57) [Claims] 1. An original slice image group storage unit that stores an original slice image group of a target object; a viewpoint direction input unit that inputs a viewpoint direction for viewing the target object; A reforming means for generating a new slice image group sliced on a plane perpendicular to the viewpoint direction; and an interest part extraction for extracting an interest part by comparing a pixel value and a predetermined threshold value with respect to the new slice image group Means, weighting means for performing a predetermined weighting operation on the extracted pixel values of the portion of interest, and hidden surface removing means for performing hidden surface removal processing by the Z-buffer method on the weighted portion of interest. An image processing apparatus comprising: